This invention relates to a vehicle control method and system for use in an automatic driving system.
To realize an automatic vehicle driving system, it is important to detect the position or speed of the vehicle.
In the conventional art, the vehicle position or speed is detected by means for directly converting the rotational speed of a wheel of the vehicle into a pulse signal to calculate the vehicle speed or the travelled distance, or means including a GPS (global positioning system) for determining the vehicle position using an artificial satellite, or means for transmitting absolute positional information stored in a marker buried in the ground, using transmission means such as a radio installation.
FIG. 1 is a conceptual view, useful in explaining the conventional automatic driving system, and showing a junction area on a highway 1. A minor road 3 meets a major road 2 at the junction. Markers 4 are buried at regular intervals along the center line of each of the major road 2 and the minor road 3. Each marker 4 stores information concerning its location, and is disposed to transmit the information to a position above the road by, for example, radio. Further, monitoring cameras 5 are provided at regular intervals at the side of the highway 1.
A vehicle 6 which travels on the road has a communication device 16 on its bottom for receiving positional information from the markers 4, and an antenna 7 on its top for receiving a GPS radio wave from an artificial satellite 8. The vehicle 6 also has, if necessary, a measuring device 30 for measuring the vehicle speed, the travelled distance, etc. by converting the rotational speed of a wheel of the vehicle into pulses and counting them. The vehicle 6 further has a controller 31 including a computer installed in the vehicle. The positional information transmitted from the marker 4 and received by the communication device 16, the information transmitted from the artificial satellite 8 and received by the antenna 7, and the vehicle speed and the travelled distance measured by the measuring device 30 are input to the vehicle controller 31, which in turn drives the vehicle 6 based on the input information.
However, the conventional method for measuring the vehicle speed and travelled distance from the pulses indicative of the rotational speed of a wheel of the vehicle 6, and controlling the vehicle based on the measurement values is considered mere auxiliary means. This is because a slip may well occur between the road and the wheels of the vehicles when the vehicle speed abruptly changes or the surface of the road becomes less suitable for driving, which makes it difficult to accurately measure the vehicle speed or travelled distance.
Moreover, although the vehicle control method using the GPS and the artificial satellite 8 is effective for wide-range positioning, it cannot be used in a tunnel or between tall buildings yet. Therefore, this method cannot singularly establish an automatic driving system and hence is only used as auxiliary means.
In addition, the conventional vehicle control method using the marker 4 is used at a branchpoint or a junction of a highway as shown in FIG. 1, at which information indicative of the accurate speed of the vehicle 6 is required. Since the marker 4 stores only fixed information concerning the position of the marker-installed position, it is not used at any place other than the branchpoint or the junction. In other words, the conventional vehicle control method using the marker 4 can be used only for limited purposes.
Even when this method is used on a road other than at a branchpoint or a junction, it imparts only positional information to a traveling vehicle, and accordingly contributes neither to automatic driving control of the vehicle, nor to the maintenance of the road.